Visual-field information collection method and system for executing the visual-field information collection method

ABSTRACT

A visual-field information collection method is capable of collecting visual-field information of a user wearing a head mounted display without applying a large calculation load to a processor. The visual-field information collection method to be executed by a processor includes arranging, in a virtual space in which a user wearing an HMD is immersed, a virtual camera that defines a visual axis for specifying a visual field of the user. The method includes determining the visual axis in accordance with one of a movement of the HMD and a line-of-sight direction of the user. The method includes determining whether or not the visual axis is moved from a predetermined first position to a predetermined second position. The method includes generating movement information representing that the visual axis is moved when the visual axis is moved from the predetermined first position to the predetermined second position.

RELATED APPLICATIONS

The present application claims priority to Japanese Application Number2016-099515, filed May 18, 2016, the disclosure of which is herebyincorporated by reference herein in its entirety.

BACKGROUND

This disclosure relates to a visual-field information collection methodand a system for executing the visual-field information collectionmethod.

For example, as disclosed in Japanese Patent Application Laid-open No.2003-248844, there is known a method involving acquiring a user's actionhistory in a game space generated by a related-art game machine, forexample, PlayStation®, and setting a land value and an advertisement feein a virtual space based on the user's action history.

The method disclosed in Japanese Patent Application Laid-open No.2003-248844 presupposes a game space generated by a related-art gamemachine, for example, PlayStation, and hence a visual-field image thatchanges in accordance with a change in user's field of view is notassumed.

Meanwhile, when the visual-field image to be visually recognized by theuser changes in accordance with a movement of a head mounted display(HMD) or the like, a large calculation load is applied to a processorconfigured to generate the visual-field image. In such a case, when alarge calculation load is required for processing of collecting user'svisual-field information data, which is executed in the background, thelimit of the calculation processing ability of the processor may beexceeded. Thus, the visual-field image may be unchangeable in accordancewith the movement of the HMD. As a result of the visual-field image notchanging in accordance with the movement of the user, the user maysuffer from virtual reality (VR) sickness.

SUMMARY

This disclosure helps to provide a visual-field information collectionmethod capable of collecting visual-field information of a user wearinga head mounted display without applying a large calculation load to aprocessor. Further, this disclosure has an object to provide a systemfor executing the visual-field information collection method.

According to at least one embodiment of this disclosure, there isprovided a visual-field information collection method to be executed bya processor. The visual-field information collection method includesarranging, in a virtual space in which a user wearing a head mounteddisplay is immersed, a virtual camera that defines a visual axis forspecifying a visual field of the user. The method further includesdetermining the visual axis in accordance with one of a movement of thehead mounted display and a line-of-sight direction of the user. Themethod further includes determining whether or not the visual axis ismoved from a predetermined first position to a predetermined secondposition. The method further includes generating movement informationrepresenting that the visual axis is moved when the visual axis is movedfrom the predetermined first position to the predetermined secondposition.

According to this disclosure, providing the visual-field informationcollection method capable of collecting the visual-field information ofthe user wearing the head mounted display without applying a largecalculation load to the processor is possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a head mounted display (HMD) systemaccording to at least one embodiment of this disclosure.

FIG. 2 is a diagram of a head of a user wearing an HMD according to atleast one embodiment of this disclosure.

FIG. 3 is a diagram of a hardware configuration of a control deviceaccording to at least one embodiment of this disclosure.

FIG. 4 is a flow chart of a method of processing for displaying avisual-field image on the HMD according to at least one embodiment ofthis disclosure.

FIG. 5 is an xyz spatial diagram of an example of a virtual space whosesurface is sectioned into a plurality of regions according to at leastone embodiment of this disclosure.

FIG. 6 is a diagram of specifying an intersection at which a visual axisof a virtual camera and the surface of the virtual space intersect witheach other based on latitude and longitude according to at least oneembodiment of this disclosure.

FIG. 7A is a yx plane diagram of the virtual space illustrated in FIG. 5according to at least one embodiment.

FIG. 7B is a zx plane diagram of the virtual space illustrated in FIG. 5according to at least one embodiment.

FIG. 8 is a flow chart of a visual-field information collection methodaccording to at least one embodiment of this disclosure.

FIG. 9 is a diagram of a state in which the intersection is moved from areference partial region to another partial region along with themovement of the visual axis of the virtual camera according to at leastone embodiment of this disclosure.

FIG. 10 is a diagram of regions in which an angular spacing betweenadjacent latitude lines and an angular spacing between adjacentlongitude lines are increased as the lines are separated from areference intersection at which a reference visual axis of the virtualcamera and the surface of the virtual space intersect with each otheraccording to at least one embodiment of this disclosure.

DETAILED DESCRIPTION

A summary of at least one embodiment of this disclosure is described.

(Item 1) A visual-field information collection method to be executed bya processor. The visual-field information collection method includesarranging, in a virtual space in which a user wearing a head mounteddisplay is immersed, a virtual camera that defines a visual axis forspecifying a visual field of the user. The method further includesdetermining the visual axis in accordance with one of a movement of thehead mounted display and a line-of-sight direction of the user. Themethod further includes determining whether or not the visual axis ismoved from a predetermined first position to a predetermined secondposition. The method further includes generating movement informationrepresenting that the visual axis is moved when the visual axis is movedfrom the predetermined first position to the predetermined secondposition.

According to the above-mentioned method, the movement information isgenerated when the visual axis is moved from the predetermined firstposition to the predetermined second position. In this manner, themovement information is not generated for all of the movements of theuser wearing the head mounted display, and hence a calculation amount ofthe processor can be reduced.

(Item 2) A visual-field information collection method according to Item(1), further including sectioning a surface of the virtual space into aplurality of regions. The method further includes determining a positionof an intersection at which the visual axis and the surface of thevirtual space intersect with each other. Determining whether or not thevisual axis is moved from the predetermined first position to thepredetermined second position includes determining whether or not theintersection is moved from a first partial region to a second partialregion among the plurality of regions. Generating the movementinformation when the intersection is moved from the first partial regionto the second partial region.

According to the above-mentioned method, the surface of the virtualspace is sectioned into the plurality of regions, and the movementinformation is generated when the intersection at which the visual axisand the surface of the virtual space intersect with each other is movedfrom the first partial region to the second partial region. In thismanner, the movement information is not generated for all of themovements of the user wearing the head mounted display, and hence thecalculation amount of the processor can be reduced.

(Item 3) A visual-field information collection method according to Item(2), further including acquiring time information representing a timewhen the intersection is moved to the second partial region when theintersection is moved from the first partial region to the secondpartial region.

According to the above-mentioned method, the time informationrepresenting the time when the intersection is moved to the secondpartial region is acquired together with the movement information, andhence the user's visual-field information can be analyzed from variousangles.

(Item 4) A visual-field information collection method according to Item(3), further including transmitting, to a server, visual-fieldinformation data generated based on a plurality of pieces of movementinformation and a plurality of pieces of time information when virtualspace data representing the virtual space is updated.

According to the above-mentioned method, the visual-field informationdata is transmitted to the server when the virtual space data isupdated. In this manner, the movement information and the timeinformation are not transmitted to the server every time the movementinformation and the time information are acquired, and hence a load ofcommunication between a user terminal and the server can be reduced.

(Item 5) A visual-field information collection method according to anyone of Items (2) to (4), further including determining a referenceintersection at which a reference visual axis, which defines a referencevisual field of the virtual camera, and the surface of the virtual spaceintersect with each other. Sectioning the surface of the virtual spaceinto the plurality of regions includes sectioning the surface of thevirtual space so that the reference intersection is prevented from beinglocated on a boundary line between the plurality of regions.

According to the above-mentioned method, the surface of the virtualspace is sectioned into the plurality of regions so that the referenceintersection is prevented from being located on the boundary linebetween the plurality of regions, and hence a situation where thecalculation load of the processor is increased as described above can beprevented.

(Item 6) A visual-field information collection method according to Item(5), in which sectioning the surface of the virtual space into theplurality of regions includes sectioning the surface of the virtualspace so that the reference intersection is located at a center of apredetermined partial region among the plurality of regions and at avicinity of the center.

According to the above-mentioned method, the surface of the virtualspace is sectioned into the plurality of regions so that the referenceintersection is located at the center of the predetermined partialregion among the plurality of regions and at the vicinity of the center,and hence a situation where the intersection is moved to a differentpartial region due to a small movement of the user wearing the headmounted display can be reduced or prevented. In this manner, a situationwhere the calculation load of the processor is increased can be reducedor prevented.

(Item 7) A visual-field information collection method according to anyone of Items (2) to (6), in which sectioning the surface of the virtualspace into the plurality of regions includes using a plurality oflatitude lines arranged at a first angular spacing and a plurality oflongitude lines arranged at a second angular spacing.

According to the above-mentioned method, a determination is maderegarding whether the intersection is moved to a different partialregion based on information relating to an angle (longitude andlatitude) of the visual axis of the virtual camera. In this manner,calculating coordinates of the intersection between the surface of thevirtual space and the visual axis is avoided, and hence the calculationamount of the processor can be reduced. That is, determining whether ornot the intersection is moved to a different partial region based on thechange in angle of the visual axis is possible. Further, each partialregion can be equally treated when the movement information is subjectedto statistical processing.

(Item 8) A visual-field information collection method according to anyone of Items (2) to (6), further including determining a referenceintersection at which a reference visual axis, which defines a referencevisual field of the virtual camera, and the surface of the virtual spaceintersect with each other. Sectioning the surface of the virtual spaceinto the plurality of regions includes using a plurality of latitudelines and a plurality of longitude lines. One of an angular spacingbetween adjacent latitude lines or an angular spacing between adjacentlongitude lines is increased as the adjacent latitude lines and theadjacent longitude lines are separated from the reference intersection.

According to the above-mentioned method, the angular spacing between theadjacent latitude lines or the angular spacing between the adjacentlongitude lines are increased as the lines are separated from thereference intersection. In this manner, the angular spacing is decreasedat a divided region in the vicinity of the reference intersection atwhich a movement of the intersection among the regions is mostfrequently observed. In this manner, the visual-field information can becollected more precisely.

(Item 9) A visual-field information collection method according to Item(1), in which determining that the visual axis is moved from thepredetermined first position to the predetermined second positionincludes determining when a maximum value of a movement amount of thevisual axis within unit time exceeds a predetermined threshold value.

According to the above-mentioned method, whether the visual axis ismoved from the predetermined first position to the predetermined secondposition when the maximum value of the movement amount of the visualaxis within unit time exceeds the predetermined threshold value isdetermined. Therefore, the movement information is not generated for allof the movements of the head mounted display, and hence the calculationamount of the processor can be reduced.

(Item 10) A system for executing the visual-field information collectionmethod of any one of Items (1) to (9).

According to the above-mentioned method, the system is capable ofcollecting the visual-field information of the user wearing the headmounted display without applying a large calculation load to theprocessor.

At least one embodiment of this disclosure is described below withreference to the drawings. Once a component is described in thisdescription of at least one embodiment, a description on a componenthaving the same reference number as that of the already describedcomponent is omitted for the sake of convenience of description.

FIG. 1 is a schematic diagram of a head mounted display (hereinaftersimply referred to as “HMD”) system 1 according to at least oneembodiment of this disclosure. As illustrated in FIG. 1, the HMD system1 includes an HMD 110 worn on a head of a user U, a position sensor 130,an external controller 320, and a control device 120.

The HMD 110 includes a display unit 112, an HMD sensor 114, headphones116, and an eye gaze sensor 140. A speaker or headphones independentfrom the HMD 110 may be used instead of providing the headphones 116 tothe HMD 110.

The display unit 112 includes a non-transmissive (or partiallytransmissive) display device configured to completely cover a field ofview (visual field) of the user U wearing the HMD 110. With this, theuser U can see only a visual-field image displayed on the display unit112, and hence the user U can be immersed in a virtual space. Thedisplay unit 112 may include a left-eye display unit configured toproject an image onto a left eye of the user U, and a right-eye displayunit configured to project an image onto a right eye of the user U.

The HMD sensor 114 is mounted near the display unit 112 of the HMD 110.The HMD sensor 114 includes at least one of a geomagnetic sensor, anacceleration sensor, and an inclination sensor (for example, an angularvelocity sensor or a gyro sensor), and can detect various movements ofthe HMD 110 worn on the head of the user U.

The eye gaze sensor 140 has an eye tracking function of detecting aline-of-sight direction of the user U. For example, the eye gaze sensor140 includes a right-eye sensor and a left-eye sensor. The right-eyesensor may be configured to detect reflective light reflected from theright eye (in particular, the cornea or the iris) of the user U byirradiating the right eye with infrared light, to thereby acquireinformation relating to a rotational angle of a right eyeball.Meanwhile, the left-eye sensor may be configured to detect reflectivelight reflected from the left eye (in particular, the cornea or theiris) of the user U by irradiating the left eye with infrared light, tothereby acquire information relating to a rotational angle of a lefteyeball.

The position sensor 130 is constructed of, for example, a positiontracking camera, and is configured to detect the positions of the HMD110 and the external controller 320. The position sensor 130 isconnected to the control device 120 so as to enable communicationto/from the control device 120 in a wireless or wired manner. Theposition sensor 130 is configured to detect information relating topositions, inclinations, or light emitting intensities of a plurality ofdetection points (not shown) provided in the HMD 110. Further, theposition sensor 130 is configured to detect information relating topositions, inclinations, and/or light emitting intensities of aplurality of detection points (not shown) provided in the externalcontroller 320. The detection points are, for example, light emittingportions configured to emit infrared light or visible light. Further,the position sensor 130 may include an infrared sensor or a plurality ofoptical cameras.

The external controller 320 is used by the user U to control, forexample, a movement of a finger object to be displayed in the virtualspace. The external controller 320 may include a right-hand externalcontroller to be used by being held by a right hand of the user U, and aleft-hand external controller to be used by being held by a left hand ofthe user U. The right-hand external controller is a device configured toindicate the position of the right hand of the user U and the movementof the fingers of the right hand of the user U. The left-hand externalcontroller is a device configured to indicate the position of the lefthand of the user U and the movement of the fingers of the left hand ofthe user U. The external controller 320 may include a plurality ofoperation buttons, a plurality of detection points, a sensor, and atransceiver.

The control device 120 is capable of acquiring information of theposition of the HMD 110 based on the information acquired from theposition sensor 130, and accurately associating the position of thevirtual camera in the virtual space with the position of the user Uwearing the HMD 110 in a real space based on the acquired information ofthe position of the HMD 110. Further, the control device 120 is capableof acquiring information of the position of the external controller 320based on the information acquired from the position sensor 130, andaccurately associating the position of the finger object to be displayedin the virtual space with a relative positional relationship between theexternal controller 320 and the HMD 110 in the real space based on theacquired information of the position of the external controller 320.

Further, the control device 120 is capable of specifying each of theline of sight of the right eye of the user U and the line of sight ofthe left eye of the user U based on the information transmitted from theeye gaze sensor 140, to thereby specify a point of gaze being anintersection between the line of sight of the right eye and the line ofsight of the left eye. Further, the control device 120 is capable ofspecifying a line-of-sight direction of the user U based on thespecified point of gaze. In this case, the line-of-sight direction ofthe user U is a line-of-sight direction of both eyes of the user U, andmatches a direction of a straight line passing through the point of gazeand a midpoint of a line segment connecting between the right eye andthe left eye of the user U.

Next, with reference to FIG. 2, a method of acquiring informationrelating to a position and an inclination of the HMD 110 is described.FIG. 2 is a diagram of the head of the user U wearing the HMD 110. Theinformation relating to the position and the inclination of the HMD 110,which are synchronized with the movement of the head of the user Uwearing the HMD 110, can be detected by the position sensor 130 and/orthe HMD sensor 114 mounted on the HMD 110. In FIG. 2, three-dimensionalcoordinates (uvw coordinates) are defined about the head of the user Uwearing the HMD 110. A perpendicular direction in which the user Ustands upright is defined as a v axis, a direction being orthogonal tothe v axis and connecting the center of the display unit 112 and theuser U is defined as a w axis, and a direction orthogonal to the v axisand the w axis is defined as a u direction. The position sensor 130and/or the HMD sensor 114 are/is configured to detect angles about therespective uvw axes (that is, inclinations determined by a yaw anglerepresenting the rotation about the v axis, a pitch angle representingthe rotation about the u axis, and a roll angle representing therotation about the w axis). The control device 120 is configured todetermine angular information for controlling a visual axis of thevirtual camera based on the detected change in angles about therespective uvw axes.

Next, with reference to FIG. 3, a hardware configuration of the controldevice 120 is described. FIG. 3 is a diagram of the hardwareconfiguration of the control device 120 and other hardware components.In FIG. 3, the control device 120 includes a control unit 121, a storageunit 123, an input/output (I/O) interface 124, a communication interface125, and a bus 126. The control unit 121, the storage unit 123, the I/Ointerface 124, and the communication interface 125 are connected to eachother via the bus 126 so as to enable communication therebetween.

The control device 120 may be constructed as a personal computer, atablet computer, or a wearable device separately from the HMD 110, ormay be built into the HMD 110. Further, a part of the functions of thecontrol device 120 may be mounted to the HMD 110, and the remaining partof functions of the control device 120 may be mounted to another deviceseparate from the HMD 110.

The control unit 121 includes a memory and a processor. The memory isconstructed of, for example, a read only memory (ROM) having variousprograms and the like stored therein and a random access memory (RAM)having a plurality of work areas in which various programs to beexecuted by the processor are stored. The processor is constructed of,for example, a central processing unit (CPU), a micro processing unit(MPU) and/or a graphics processing unit (GPU), and is configured todevelop, on the RAM, instructions designated by various programsinstalled into the ROM to execute various types of processing incooperation with the RAM.

In particular, the control unit 121 may control various operations ofthe control device 120 by causing the processor to function, with theRAM, as a display control system (to be described later) for executing adisplay control method according to at least one embodiment. The controlunit 121 executes a predetermined application (game program) stored inthe memory or the storage unit 123 to provide a virtual space(visual-field image) on the display unit 112 of the HMD 110. With this,the user U can be immersed in the virtual space displayed on the displayunit 112.

The storage unit (storage) 123 is a storage device, for example, a harddisk drive (HDD), a solid state drive (SSD), or a USB flash memory, andis configured to store instructions and various types of data (forexample, virtual-space data or visual-field information data). Thedisplay control system may be incorporated into the storage unit 123.Further, the storage unit 123 may store instructions for authenticationof the user U and game programs including data relating to variousimages and objects. Further, a database including tables for managingvarious types of data may be constructed in the storage unit 123.

The I/O interface 124 is configured to connect each of the positionsensor 130, the HMD 110, and the external controller 320 to the controldevice 120 so as to enable communication therebetween, and isconstructed of, for example, a universal serial bus (USB) terminal, adigital visual interface (DVI) terminal, or a high-definition multimediaInterface® (HDMI) terminal. The control device 120 may be wirelesslyconnected to each of the position sensor 130, the HMD 110, and theexternal controller 320.

The communication interface 125 is configured to connect the controldevice 120 to a communication network 3, for example, a local areanetwork (LAN), a wide area network (WAN), or the Internet. Thecommunication interface 125 includes various wire connection terminalsand various processing circuits for wireless connection forcommunication to/from an external device, for example, a server 30, viathe communication network 3, and is configured to adapt to communicationstandards for performing communication via the communication network 3.

Next, with reference to FIG. 4, FIG. 5, FIG. 7A, FIG. 7B, processing fordisplaying the visual-field image on the HMD 110 is described. FIG. 4 isa flow chart of a method of processing of displaying the visual-fieldimage on the HMD 110. FIG. 5 is an xyz spatial diagram of an example ofa virtual space 200. FIG. 7A is a yx plane diagram of the virtual space200 in FIG. 5. FIG. 7B is a zx plane diagram of the virtual space 200 inFIG. 5.

In FIG. 4, in Step S1, the control unit 121 (see FIG. 3) generatesvirtual space data representing the virtual space 200 in which a virtualcamera 300 is arranged. In FIG. 5, the virtual space 200 is defined as acelestial sphere having a center position as the center (in FIG. 5, onlythe upper-half of the celestial sphere is shown in FIG. 5 for clarity).Further, in the virtual space 200, an xyz coordinate system having thecenter position as the origin is set. In the initial state of the HMDsystem 1, the virtual camera 300 is arranged at the center position ofthe virtual space 200. The uvw coordinate system that defines the visualfield of the virtual camera 300 is determined so as to synchronize withthe uvw coordinate system that is defined about the head of the user Uin the real space. Further, the virtual camera 300 may be moved in thevirtual space 200 in synchronization with the movement in the real spaceof the user U wearing the HMD 110.

Next, in Step S2, the control unit 121 specifies a visual field CV (seeFIG. 7A and FIG. 7B) of the virtual camera 300. Specifically, thecontrol unit 121 acquires information relating to a position and aninclination of the HMD 110 based on data representing the state of theHMD 110, which is transmitted from the position sensor 130 and/or theHMD sensor 114. Next, the control unit 121 determines the position andthe direction of the virtual camera 300 in the virtual space 200 basedon the information relating to the position and the inclination of theHMD 110. Next, the control unit 121 determines a visual axis L of thevirtual camera 300 based on the position and the direction of thevirtual camera 300, and specifies the visual field CV of the virtualcamera 300 based on the determined visual axis L. In this case, thevisual field CV of the virtual camera 300 corresponds to a part of theregion of the virtual space 200 that can be visually recognized by theuser U wearing the HMD 110 (in other words, corresponds to a part of theregion of the virtual space 200 to be displayed on the HMD 110).Further, the visual field CV has a first region CVa set as an angularrange of a polar angle α about the visual axis L in the xy planeillustrated in FIG. 7A, and a second region CVb set as an angular rangeof an azimuth R about the visual axis L in the xz plane illustrated inFIG. 7B. The control unit 121 may specify the line-of-sight direction ofthe user U based on data representing the line-of-sight direction of theuser U, which is transmitted from the eye gaze sensor 140, and maydetermine the direction of the virtual camera 300 based on theline-of-sight direction of the user U.

As described above, the control unit 121 can specify the visual field CVof the virtual camera 300 based on the data transmitted from theposition sensor 130 and/or the HMD sensor 114. In this case, when theuser U wearing the HMD 110 moves, the control unit 121 can change thevisual field CV of the virtual camera 300 based on the data representingthe movement of the HMD 110, which is transmitted from the positionsensor 130 and/or the HMD sensor 114. That is, the control unit 121 canchange the visual field CV in accordance with the movement of the HMD110. Similarly, when the line-of-sight direction of the user U changes,the control unit 121 can move the visual field CV of the virtual camera300 based on the data representing the line-of-sight direction of theuser U, which is transmitted from the eye gaze sensor 140. That is, thecontrol unit 121 can change the visual field CV in accordance with thechange in the line-of-sight direction of the user U.

Next, in Step S3, the control unit 121 generates visual-field image datarepresenting the visual-field image to be displayed on the display unit112 of the HMD 110. Specifically, the control unit 121 generates thevisual-field image data based on the virtual space data defining thevirtual space 200 and the visual field CV of the virtual camera 300.

Next, in Step S4, the control unit 121 displays the visual-field imageon the display unit 112 of the HMD 110 based on the visual-field imagedata. As described above, the visual field CV of the virtual camera 300changes in accordance with the movement of the user U wearing the HMD110, and thus the visual-field image to be displayed on the display unit112 of the HMD 110 changes as well. Thus, the user U can be immersed inthe virtual space 200.

The virtual camera 300 may include a left-eye virtual camera and aright-eye virtual camera. In this case, the control unit 121 generatesleft-eye visual-field image data representing a left-eye visual-fieldimage based on the virtual space data and the visual field of theleft-eye virtual camera. The control unit 121 generates right-eyevisual-field image data representing a right-eye visual-field imagebased on the virtual space data and the visual field of the right-eyevirtual camera. Then, the control unit 121 displays the left-eyevisual-field image and the right-eye visual-field image on the displayunit 112 of the HMD 110 based on the left-eye visual-field image dataand the right-eye visual-field image data. In this manner, the user Ucan visually recognize the visual-field image as a three-dimensionalimage from a combination of the left-eye visual-field image and theright-eye visual-field image. For the sake of convenience ofdescription, the number of the virtual cameras 300 is one herein. As amatter of course, at least one embodiment of this disclosure is alsoapplicable to a case where the number of the virtual cameras is morethan one.

Next, the visual-field information collection method according to atleast one embodiment is described with reference to FIG. 5, FIG. 8, andFIG. 9. FIG. 8 is a flow chart of a visual-field information collectionmethod according to at least one embodiment. FIG. 9 is a diagram of astate in which an intersection C at which the visual axis L of thevirtual camera 300 and a surface S of the virtual space 200 intersectwith each other is moved from a reference partial region Rref to adifferent partial region R1 along with the movement of the visual axis Lof the virtual camera 300.

In FIG. 5 and FIG. 9, for the sake of convenience of description,latitude lines lo and longitude lines la on the front side (−z side) ofthe surface S of the virtual space 200 are not shown for clarity.Latitude lines lo and longitude lines la and a plurality of regions R onthe deep side (+z side) of the surface S of the virtual space 200 areshown.

In FIG. 8, in Step S10, the control unit 121 (see FIG. 3) generatesvirtual space data representing the virtual space 200 in which thevirtual camera 300 is arranged. Step S10 is the same as Step S1 of FIG.4 and the description is not repeated for the sake of brevity.

Next, in Step S11, the control unit 121 determines a referenceintersection Cref (see FIG. 5) at which a reference visual axis Lref,which defines a reference visual field of the virtual camera 300, andthe surface S of the virtual space 200 intersect with each other. Inthis case, the reference visual field refers to a visual field in theinitial state of the virtual camera 300. Further, the reference visualaxis Lref refers to a visual axis L in the initial state of the virtualcamera 300.

Next, in Step S12, the control unit 121 sections the surface S of thevirtual space 200 into the plurality of regions R with use of latitudelines lo arranged at a predetermined angular spacing relative to virtualcamera 300 and longitude lines la arranged at a predetermined angularspacing relative to virtual camera 300. In other words, the control unit121 sets the plurality of regions R on the surface S by providing a gridformed of the latitude lines lo and the longitude lines la on thesurface S of the spherical virtual space 200.

Regarding this point, the control unit 121 sections the surface S of thevirtual space 200 into the plurality of regions R so that the referenceintersection Cref is prevented from being located on a boundary line(that is, on any latitude line lo or any longitude line la) between theplurality of regions R. In at least one embodiment, the control unit 121sections the surface S of the virtual space 200 into the plurality ofregions R so that the reference intersection Cref is located at a centerof a predetermined partial region among the plurality of regions R andat a vicinity of the center. In this case, a partial region R in whichthe reference intersection Cref is present is referred to as “referencepartial region Rref”.

Further, the number of the latitude lines lo is set in accordance withan angular spacing between adjacent latitude lines lo. For example, whenthe angular spacing between the adjacent latitude lines lo is 15°,(90°/15°)−1=5 is obtained, and hence the number of the latitude lines loin virtual space 200 is set as 5. Similarly, the number of the longitudelines la is set in accordance with the angular spacing between adjacentlongitude lines la. For example, when the angular spacing between theadjacent longitude lines la is 15°, 360°/15°=24 is obtained, and hencethe number of the longitude lines la in virtual space 200 is set as 24.The control unit 121 can set the number of the latitude lines lo and thenumber of the longitude lines la as appropriate based on the type of thevirtual space data.

Further, the number of the regions R is determined based on the numberof the longitude lines la and the number of the latitude lines lo. Forexample, when the number of the longitude lines la is n and the numberof the latitude lines lo is m, a total number N of the regions R isN=n×(m+1) (provided that n≧2).

Next, in Step S13, the control unit 121 determines whether or not theHMD 110 is moved. Specifically, the control unit 121 may determine thatthe HMD 110 is moved by receiving data representing the state of the HMD110 from the position sensor 130 and/or the HMD sensor 114.Alternatively, the control unit 121 may acquire information relating tothe position and the inclination of the HMD 110 based on the datarepresenting the state of the HMD 110, which is transmitted from theposition sensor 130 and/or the HMD sensor 114, and determine whether ornot the HMD 110 is moved based on the acquired information.

When the control unit 121 determines that the HMD 110 is moved (YES inStep S13), the control unit 121 updates the position and the directionof the virtual camera 300 in the virtual space 200, and determines theposition of the intersection C at which the moved visual axis L of thevirtual camera 300 and the surface S of the virtual space 200 intersectwith each other (Step S14). For example, under a state in which thevirtual camera 300 is arranged at the center position of the virtualspace 200, the intersection C is determined based on a radius r of thevirtual space 200, and on a latitude θ and a longitude p of the visualaxis L illustrated in FIG. 6. In this case, the radius r of the virtualspace 200 has a known value, and hence the control unit 121 determinesthe intersection C based on the latitude 9 and the longitude p of thevisual axis L. On the other hand, when the control unit 121 determinesthat the HMD 110 is not moved (NO in Step S13), the processing returnsto Step S13.

In Step S13, the control unit 121 determines whether or not the HMD 110is moved, but alternatively, the control unit 121 may determine whetheror not a line-of-sight direction of the user U is changed. In this case,the control unit 121 may receive information from the eye gaze sensor140 to determine that the line-of-sight direction of the user U ischanged. Alternatively, the control unit 121 may acquire informationrelating to the line-of-sight direction of the user U based oninformation transmitted from the eye gaze sensor 140, and determinewhether or not the line-of-sight direction of the user U is changedbased on the acquired information. In at least one embodiment, thecontrol unit 121 updates the position and direction of virtual camera300 in response to a change in the light-of-sight direction of the userU.

Next, in Step S15, the control unit 121 determines whether or not theintersection C is moved to a different partial region R. For example,when the control unit 121 determines that, in FIG. 9, the intersection Cis moved from the reference partial region Rref (first partial region)to the partial region R1 (second partial region) (YES in Step S15), thecontrol unit 121 acquires movement information representing that theintersection C is moved to the partial region R1 (that is, informationrepresenting a partial region at a movement destination), and timeinformation representing the time when the intersection C is moved tothe partial region R1 (Step S16). On the other hand, when the controlunit 121 determines that the intersection C is not moved to a differentpartial region R (that is, when the control unit 121 determines that theintersection C stays at the same partial region R), the processingreturns to Step S13.

In this case, the partial region R is defined based on the latitudelines lo and the longitude lines la, and hence each partial region R hasan angular range of the latitude θ and the longitude φ. Further, asdescribed above, the intersection C is determined based on the latitudeθ and the longitude φ of the visual axis L. In this manner, the controlunit 121 can determine whether or not the intersection C is moved to adifferent partial region R without performing complicated calculation bydetermining the latitude θ and the longitude φ of the moved visual axisL.

Next, in Step S17, the control unit 121 updates the visual-fieldinformation data stored in the storage unit 123. An example of thevisual-field information data is shown below.

TABLE 1 <Visual-field information data> Partial region R at movementUser ID destination Staying duration T X R1 10 seconds R2  5 seconds . .. . . .

In this case, the visual-field information data includes informationrelating to the user ID of the user U, the partial region R at themovement destination, and a staying duration T during which theintersection stays in the partial region R at the movement destination.For example, when the intersection C is moved from the reference partialregion Rref to the partial region R1 at a time t1, and is then movedfrom the partial region R1 to a partial region R2 at a time t2, thecontrol unit 121 determines the staying duration T in the partial regionR1 at the movement destination based on the time t1 and the time t2(that is, by subtracting the time t1 from the time t2). After that, thecontrol unit 121 updates the content of the visual-field informationdata stored in the storage unit 123 based on the information relating tothe partial region R1 at the movement destination and the stayingduration T (T=t2−t1) in the partial region R1. The control unit 121 mayupdate the visual-field information data based on the informationrelating to the partial region R1 when the partial region R1 at themovement destination is determined, and then update the visual-fieldinformation data again based on the information relating to the stayingduration T when the staying duration T in the partial region R1 isdetermined. As described above, the visual-field information data isgenerated based on a plurality of pieces of movement information and aplurality of pieces of time information.

Next, in Step S18, the control unit 121 determines whether or not thevirtual space data is to be updated. For example, when the control unit121 determines that the scene of the virtual space 200 is to beswitched, the control unit 121 determines that the virtual space data isto be updated. After that, when the control unit 121 determines that thevirtual space data is to be updated (YES in Step S18), the control unit121 transmits the visual-field information data stored in the storageunit 123 to the server 30 via the communication interface 125 and thecommunication network 3 (Step S19), and then updates the virtual spacedata (Step S20). On the other hand, when the control unit 121 determinesthat the virtual space data is not to be updated (NO in Step S18), theprocessing returns to Step S13.

According to at least one embodiment, the surface S of the virtual space200 is sectioned into the plurality of regions R. Then, when theintersection C at which the visual axis L of the virtual camera 300 andthe surface S of the virtual space 200 intersect with each other ismoved to a different partial region R, the movement informationrepresenting that the intersection C is moved to a different partialregion R is generated. On the other hand, when the intersection C ismoved within the same partial region R, the movement information is notgenerated. In this manner, the movement information is not generated forall of the movements of the user U wearing the HMD 110, and hence thecalculation amount of the control unit 121 (processor) can be reduced.

Further, the surface S of the virtual space 200 is sectioned into theplurality of regions R with use of the latitude lines lo and thelongitude lines la, and hence determining whether or not theintersection C is moved to a different partial region R based on theinformation relating to the change in angle (latitude θ and longitude φ)of the visual axis L of the virtual camera 300. In this manner, thecalculation amount of the control unit 121 can be reduced. Further, eachpartial region R can be equally treated when the movement information issubjected to statistical processing.

Further, the time information representing the time when theintersection C is moved to a different partial region R is acquiredtogether with the movement information, and hence the visual-fieldinformation of the user U can be analyzed from various angles. Inparticular, when the information relating to the staying duration T inthe partial region R at the movement destination is analyzed, the regionin the virtual space 200 which is paid attention to by each user can beanalyzed. Further, when the staying duration T exceeds a threshold, theuser U is determined to not be wearing the HMD 110. In at least oneembodiment, the threshold is 30 seconds, 1 minute, 2 minutes or anothersuitable threshold. In this manner, the staying duration T that exceedsthe threshold may be removed from an activation time of the HMD 110, tothereby estimate a duration during which the user U is actually wearingthe HMD 110.

Further, the visual-field information data of each user is transmittedto the server 30 via the communication network 3. In this manner, thevisual-field information data of each user, which is transmitted to theserver 30, can be utilized as big data, to thereby analyze a focusedregion or a non-focused region in the virtual space 200. In this manner,for example, an optimum layout of the object in the virtual space 200can be determined based on the visual-field information data. Further,the user's behavior in the virtual space 200 can be analyzed.

Further, according to at least one embodiment, the visual-fieldinformation data is transmitted to the server 30 when the virtual spacedata is updated. In this manner, the movement information and the timeinformation are not transmitted to the server 30 every time the movementinformation and the time information are acquired, and hence a load ofcommunication between the HMD system 1 (user terminal) and the server 30can be reduced.

Further, the surface S of the virtual space 200 is sectioned into theplurality of regions R so that the reference intersection Cref isprevented from being located on the boundary line (that is, on thelatitude line lo or the longitude line la) between the plurality ofregions R. Regarding this point, for example, when the referenceintersection Cref is located on the boundary line (latitude line lo orlongitude line la) between the plurality of regions R, the intersectionC is frequently moved to a different partial region R in accordance witha small movement of the user U wearing the HMD 110. Therefore, thecontrol unit 121 (processor) frequently acquires the movementinformation and the time information, and hence the calculation load ofthe control unit 121 is increased. On the other hand, when the referenceintersection Cref is not located on the boundary line (that is, on thelatitude line lo or the longitude line la) between the plurality ofregions R, the above-mentioned situation where the calculation load ofthe control unit 121 is increased can be reduced or prevented. Inparticular, when the reference intersection Cref is located at thecenter of the reference partial region Rref and at the vicinity of thecenter, a situation where the intersection C is frequently moved to adifferent partial region R in accordance with a small movement of theuser U can be suitably prevented.

Further, in at least one embodiment, in FIG. 5 and FIG. 8, the angularspacing between the adjacent latitude lines lo and the angular spacingbetween the adjacent longitude lines la are fixed, but the angularspacing between the adjacent latitude lines lo and/or the angularspacing between the adjacent longitude lines la may not be fixed. Forexample, as illustrated in FIG. 10, the angular spacing between theadjacent longitude lines la may be increased as the longitude lines laare separated from the reference intersection Cref. Similarly, theangular spacing between the adjacent latitude lines lo may be increasedas the latitude lines lo are separated from the reference intersectionCref. In this manner, a partial region R close to the referenceintersection C (including the reference partial region Rref) is formedto be smaller than a partial region R separated from the referenceintersection Cref. As a result, the visual-field information data can becollected more precisely.

Further, in order to achieve various types of processing to be executedby the control unit 121 with use of software, the display control systemfor executing the display control method of at least one embodiment mayinclude instructions installed in advance into the storage unit 123 orthe ROM. Alternatively, the instructions for execution by the displaycontrol system may be stored in a computer-readable storage medium, forexample, a magnetic disk (HDD or a floppy disk), an optical disc (forexample, CD-ROM, DVD-ROM, and Blu-ray disc), a magneto-optical disk (forexample, MO), and a flash memory (for example, an SD card, a USB memory,and an SSD). In this case, the storage medium is connected to thecontrol device 120, and thus the instructions stored in the storagemedium is installed into the storage unit 123. Then, the instructionsfor the display control system are installed in the storage unit 123 isloaded onto the RAM, and the processor executes the loaded program. Inthis manner, the control unit 121 executes the display control method ofat least one embodiment.

Further, the instructions for the display control system may bedownloaded from a computer on the communication network 3 via thecommunication interface 125. Also in this case, the downloadedinstructions are similarly installed into the storage unit 123.

This concludes description of at least one embodiment of thisdisclosure. However, the description of at least one embodiment is notto be read as a restrictive interpretation of the technical scope ofthis disclosure. The at least one embodiment described is merely givenas an example, and a person skilled in the art would understand thatvarious modifications can be made to at least one embodiment within thescope of this disclosure set forth in the appended claims. Thus, thetechnical scope of this disclosure is to be defined based on the scopeof this disclosure set forth in the appended claims and an equivalentscope thereof.

For example, in at least one embodiment, the surface S of the virtualspace 200 is sectioned into the plurality of regions R with use of thelatitude lines lo and the longitude lines la, but the movement of thevisual axis L of the virtual camera 300 may be determined withoutsectioning the surface S of the virtual space 200 into the plurality ofregions R. That is, the control unit 121 may determine whether or notthe visual axis L is moved from a predetermined first position to apredetermined second position, and when the control unit 121 determinesthat the visual axis L is moved from the predetermined first position tothe predetermined second position, the movement information (forexample, coordinates of the moved intersection C) representing that thevisual axis L is moved, and the time information representing the timewhen the visual axis L is moved may be acquired. Regarding this point,when the visual axis L is moved in accordance with the movement of theuser U wearing the HMD 110, the control unit 121 determines whether ornot the maximum value of a movement amount of the visual axis L withinunit time exceeds a predetermined threshold value. Then, when thecontrol unit 121 determines that the maximum value of the movementamount of the visual axis L within unit time exceeds the predeterminedthreshold value, the control unit 121 may acquire the movementinformation and the time information (Step S16 of FIG. 8). On the otherhand, when the control unit 121 determines that the maximum value of themovement amount of the visual axis L within unit time does not exceedthe predetermined threshold value, the processing may return to Step S13of FIG. 8. In this case, similarly, the movement information and thetime information are not generated for all of the movements of the userU wearing the HMD 110, and hence the calculation amount of the controlunit 121 can be reduced.

What is claimed is:
 1. A method comprising: defining a virtual space inwhich a user wearing a head mounted display (HMD) is immersed;determining a visual axis in accordance with at least one of a movementof the HMD or a line-of-sight direction of the user; specifying a visualfield of the user in the virtual space in accordance with the visualaxis; sectioning a surface of the virtual space into a plurality ofregions; determining a position of an intersection at which the visualaxis and the surface of the virtual space intersect with each other;determining whether the intersection moved from a first region of theplurality of regions to a second region of the plurality of regions;generating movement information in response to the determination thatthe intersection moved from the first region to the second region;acquiring time information representing a time when the intersectionmoved to the second region in response to the determination that theintersection moved from the first region to the second region; andtransmitting, to a server, visual-field information data generated basedon the movement information and the time information; and updatingvirtual space data, which represents the virtual space.
 2. Thevisual-field information collection method according to claim 1, furthercomprising: determining a reference intersection at which a referencevisual axis, which defines a reference visual field, and the surface ofthe virtual space intersect with each other, wherein sectioning thesurface of the virtual space into the plurality of regions comprisessectioning the surface of the virtual space so that the referenceintersection is prevented from being located on a boundary line betweenthe plurality of regions.
 3. The visual-field information collectionmethod according to claim 2, wherein sectioning the surface of thevirtual space into the plurality of regions comprises sectioning thesurface of the virtual space so that the reference intersection islocated at a center of a predetermined region among the plurality ofregions and at a vicinity of the center.
 4. The visual-field informationcollection method according to claim 1, wherein sectioning the surfaceof the virtual space into the plurality of regions comprising sectioningthe surface of the virtual space using a plurality of latitude linesarranged at a first angular spacing and a plurality of longitude linesarranged at a second angular spacing.
 5. The visual-field informationcollection method according to claim 1, further comprising: determininga reference intersection at which a reference visual axis, which definesa reference visual field, and the surface of the virtual space intersectwith each other, wherein sectioning the surface of the virtual spaceinto the plurality of regions comprises sectioning the virtual spaceusing a plurality of latitude lines and a plurality of longitude lines,and one of an angular spacing between adjacent latitude lines or anangular spacing between adjacent longitude lines is increased as adistance between the adjacent latitude lines and the referenceintersection or a distance between the adjacent longitude lines and thereference intersection increases.
 6. A system comprising: a processor;and a non-transitory computer readable medium connected to theprocessor, wherein the processor is configured to execute instructionsstored on the non-transitory computer readable medium for: defining avirtual space in which the a user wearing a head mounted display (HMD)is immersed; determining a visual axis in accordance with at least oneof a movement of the HMD or a line-of-sight direction of the user;specifying a visual field of the user in the virtual space in accordancewith the visual axis; sectioning a surface of the virtual space into aplurality of regions; determining a position of an intersection at whichthe visual axis and the surface of the virtual space intersect with eachother; determining whether the intersection moved from a first region ofthe plurality of regions to a second region of the plurality of regions;generating movement information in response to the determination thatthe intersection moved from the first region to the second region;acquiring time information representing a time when the intersectionmoved to the second region in response to the determination that theintersection moved from the first region to the second region; andtransmitting, to a server, visual-field information data generated basedon the movement information and the time information; and updatingvirtual space data, which represents the virtual space.